2 P42s, a few Amfleets, maybe 1-2 other private cars, and the GA 300 on the back w/Obama. That's my guess.
That was pretty much the primary train's consist: 2 P42s, 3 Amfleet IIs (one of which was a cafe, I think?), GA 300. Short and to the point, and the Amfleets were all for the press, of course.
Given that the inauguration train has ten families of guests, I expect a second private car will be in the consist for them (since they may represent upwards of 20-30 passengers). Obama's car will carry him, Michelle, Sasha and Malia and Marian Robinson (unless they're staying in DC), Joe and Jill Biden, Reggie Love (Obama's "body man"), five or six other SS agents, and maybe Axelrod or another advisor or two plus several aides (Herbie and Marvin, if they're still working for him, perhaps); and Obama and Biden and their wives will circulate into the family guests car (which will have another 5 or 6 SS agents), and a few press photographers will be allowed in there; they may or may not allow any press into GA 300 or whatever observation they're using. (I do hold out hope for PA 120...) At least, that's my guess based on how similar events ran during the campaign.
Believe it or not, early in the campaign (through April at least) Obama's motorcade drivers were not SS agents--they were local volunteers! The SS ran background checks, of course, but locals were chosen because they knew the area roads better than any SS agent would. Generally, SUV 1 had local driver, Herbie (motorcade manager), Obama, Reggie, and a couple more SS agents; SUV 2 had local driver, Marvin (scheduling manager), Axelrod, and several SS agents. Not always exactly that "consist", but that was how it was for the events I helped with. I'm sure it's not that way now!